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what is kalvin and color temperature?


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#1 ramesh bhatnagar

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Posted 27 February 2009 - 09:44 AM

hello david sir, how r u? pls teach me what is Kalvin? how its works? hows is count? what is color temperature? what is relation of kalvin and color temperature?
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#2 K Borowski

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Posted 27 February 2009 - 10:10 AM

Well, I'm not David, but let me give you a quick explanation:

K*e*lvin is basically a description based on the absolute temperature scale equivalent, of the Celsius temperature of how hot you would have to heat a "black body", like an iron rod in an oven, to get it to emit a certain color of light.

It basically has to do with the warmth or coolness of the "white" of the light your black body is emitting.

Counter-intuitively, the "hotter" the Kelvin temperature gets, the "cooler" the light gets (you get more perceived blue the higher the number goes and more red the lower the Kelvin temperature goes).

One of the drawbacks of Kelvin is that the number isn't proportional depending on what temperature you are at. In simple English the lower the temperature is, the more perceptable a 100-degree shift will be. So, if you are going from say 5600K to 6000K, the shift will actually be much smaller than, say, 2600 to 3000K.

To counter this non-arithmetic behavior, taking the MIcro-REciprocal Degree measurement (MIRED), effectively cancels out this behavior and renders an (almost) absolute filtration change factor that is sometimes used with colored glass filters. So basically, just think of MIRED as another way of expressing Kelvin in terms of an absolute filtration change factor (micro-reciprocal is a fancy way of saying Kelvin times the inverse of a million: 1/1,000,000).

I didn't 'do a good job of putting that in simple English, but hopefully that is clear-enough for you!

One last note, here are a couple of approximate Kelvin temperatures of different light sorces:

Light bulbs: Under 3,000K (the lower the wattage, the lower the Kelvin temperature)

Movie lights: 3,200K

Type A amateur photoflood lighting: 3,400K

Fluorescent lighting: ~4,000K (varies with different types)

Direct sunlight: 5,500K

Skylight (shade or cloudy): 6,000 to up to 10,000K

So, notice how the Kelvin number climbs "faster" and "faster" the higher up the scale you get, hence the need for MIRED. While a 3,200 to 3,400K change might be enough to necessitate putting a correction filter on a lens with tungsten (3,200K-balanced) film, a 5,500K to 6,000K will often be small enough to be shot un-filtered.
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#3 K Borowski

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Posted 27 February 2009 - 10:52 AM

I'll chalk up your re-asking this question to your mis-spelling of the word "Kelvin" and what I'm assuming to be your learning English as a second language, but this topic has already been talked about to death by David Mullen and others:

http://www.cinematog...h...2&hl=kelvin

http://www.cinematog...h...3&hl=kelvin

http://www.cinematog...h...7&hl=kelvin


Please consider using the "Search" button (right under the cinematography.com banner at the top of the page, next to "Forum Guidelines" and "Members" before making further posts for basic cinematography information.
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#4 Ryan Patrick OHara

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Posted 01 March 2009 - 07:29 PM

http://www.cinematog...showtopic=36251
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